The aim of this project is to determine the mechanisms by which neurons insure an adequate supply of functionally important proteins in the face of fluctuating levels of activity. These investigations are being carried out in the simple nervous system of the mollusk, Aplysia, using several identified single neurosecretory cells and cell groups, because this preparation allows the use of in vitro techniques and the control of variables to a degree that would not be possible in other systems. Kinetic and pharmacological studies are being used to investigate the processes of intracellular storage and compartmentation of neurosecretory material and other axonally transported proteins. Kinetic and peptide mapping studies are being used to define the proteolytic processing sequences by which these cells produce their secretory products. Factors influencing the rate of synthesis of neurosecretory proteins in accord with secretory demand are being investigated, and studies will be undertaken to determine if neuronal activity in a peptidergic pathway has any influence on the rate or quantity of axonal transport of secretory peptides.